MARCASITE specimen mar-11
Dims: 4.8 x 3.9 x 1.9" (12.2 x 9.9 x 4.8 cm)
Wt: 1 lb., 9.6 oz. (727 g)
Amax Mine, Reynolds County, Missouri, U.S.A.
The documentation for this specimen stated that it is made of Marcasite and pyrite, but I believe that pseudomorphing has likely occurred, and that the piece is mostly Marcasite by weight, though I could be wrong. It consists of a thick crust of intergrown "pyrite" pyritohedrons that are covered with a thinner crust of intergrown Marcasite crystals. There are hundreds of these tiny Marcasites, which do not appear to exceed 0.2" (5 mm) in length- actually, most of them do not seem to exceed 0.1" (3 mm). They are generally not very exposed, and so are in excellent condition, showing only a small amount of damage. All have excellent orthorhombic prismatic form, with many of them clustered together in almost "cockscomb" formations. All have a dull, pale golden coloration and the standard metallic luster. The "pyrites" on which they rest also show excellent form, with well-defined edges and clean faces. These crystals range in diameter from 0.2" (5 mm) to 1.0" (2.5 cm) or more, though most are covered with the Marcasite crust. Many are incomplete, likely due to damage incurred during mining. The underside of the specimen shows excellent evidence of the crystalline nature of the crust, with many flat, geometric faces and indentations, as there is no host rock present.